How to Winterize Your Plumbing: 7 Steps
Puget Sound winters are mild most of the time, which is exactly what makes them dangerous for plumbing. We go weeks above freezing, homeowners stop thinking about it, and then a cold snap drops overnight temperatures into the teens for three days, and the calls start.
A burst supply line can put hundreds of gallons into a house before anyone notices. Preventing it takes an afternoon and costs almost nothing.
By Ramin Shahbaziasl, Owner, Eastside Repipe & Plumbing · Last updated July 15, 2025
Here is the sequence we walk homeowners through across Bellevue and the Eastside every fall.
The seven steps:
Drain outdoor plumbing
Insulate pipes in unheated spaces
Seal gaps where cold air gets in
Flush the water heater
Locate your main shutoff valve
Drip faucets during a hard freeze
Book a pre-winter inspection
Step 1: Drain Outdoor Plumbing
Hose bibs, spigots, and irrigation lines freeze first because they sit fully exposed with no heated space around them.
Disconnect every garden hose and store them inside
Close the interior shutoff valve that feeds each outdoor faucet
Open the outdoor faucet and let it drain completely, so any water left has room to expand
Blow out or drain the irrigation system before the first freeze
Fit insulated covers over hose bibs that have no interior shutoff
If your home has a dedicated shutoff for outdoor plumbing, close it and drain the line rather than relying on the faucet alone.
Step 2: Insulate Pipes in Unheated Spaces
Crawl spaces, garages, attics, and exterior walls are where pipes actually freeze. Pipes under sinks on outside walls are the ones most people forget.
What to use:
Foam pipe sleeves sized to the pipe diameter, which are inexpensive and take minutes per run
UL-listed heat tape or heat cable on the most exposed runs. The listing matters. Non-listed or badly installed heat tape is a known fire cause, so follow the manufacturer's instructions exactly
Fiberglass wrap in larger unheated areas
Two free things that help:
Keep the garage door shut if supply lines run through it
Open kitchen and bathroom cabinet doors during a cold snap so room heat reaches the pipes inside. Move cleaners and chemicals out of children's reach first, since those cabinets are usually closed for a reason
If your pipes are old enough that insulation is only buying time, repiping is the permanent answer. Our comparison of PEX vs copper covers the material choice.
Step 3: Seal Gaps Where Cold Air Gets In
Insulation on the pipe does not help much if freezing air is blowing straight onto it.
Walk the perimeter and look for daylight around anywhere plumbing enters the house, plus dryer vents, foundation vents, and crawl space access panels. Fill small gaps with caulk and larger ones with expanding foam.
A single unsealed penetration on the windward side can drop the temperature in a crawl space enough to freeze a pipe that would otherwise be fine.
Step 4: Flush the Water Heater
Sediment at the bottom of the tank makes the unit work harder right when you are asking the most of it.
Draining a few gallons off clears it. Two cautions before you start: the water coming out is scalding, and on a unit that has not been drained in years, the valve sometimes fails to reseal afterward. If yours is older, or you are not confident, this is a reasonable one to hand off.
If the heater is already struggling, our guide to water heater warning signs covers whether to repair or replace before winter rather than during it.
Step 5: Locate Your Main Shutoff Valve
This is the step that saves the most money and takes the least time.
Find the main shutoff now, confirm it actually turns, and make sure everyone in the household knows where it is. In most Eastside homes, it is near the water meter or where the main line enters, which usually means a crawl space, garage, or basement wall.
A valve that has not moved in fifteen years is worth discovering on a dry afternoon rather than at 2 am with water coming through a ceiling.
Going away for a while? Set the thermostat no lower than 55°F. For longer absences, shut the water off at the main and drain the system.
Step 6: Drip Faucets During a Hard Freeze
Moving water is much harder to freeze than still water, and a trickle is enough.
When to start: the working threshold is 20°F. Pipes generally begin freezing below that, though uninsulated pipes in uninsulated spaces can freeze at higher temperatures, and wind chill on an exposed crawl space brings it on faster.
Which faucets: the Red Cross recommends letting the cold water drip from faucets served by exposed pipes, not every tap in the house. Prioritize fixtures on exterior walls and the ones furthest from where the main enters.
How much: a slow, steady drip. You are not trying to run the tap.
Leave it going until temperatures climb back above freezing, not just until morning.
Step 7: Book a Pre-Winter Inspection
DIY prep handles what you can see. An inspection finds what you cannot: pipe runs through unheated voids you did not know existed, corrosion narrowing a supply line, a shutoff valve that will not close when you need it.
We check the vulnerable runs, test the main shutoff, look at the water heater, and tell you what actually needs doing before the first freeze rather than selling you a package.
If you are getting quotes, verify whoever you hire. Washington plumbing work must be done by certified plumbers employed by a licensed contractor, and you can check any company's license, bond, and insurance status for free through the state Department of Labor and Industries.
We cover Bellevue, Kirkland, Redmond, and Seattle. See the full service area.
Worth Adding: Smart Thermostats and Leak Detectors
A smart thermostat holds a steady interior temperature and lets you check on the house remotely, which matters most when you are away during a cold stretch.
Water leak detectors are the better buy. A sensor placed near the water heater, under sinks, and in the crawl space costs very little and alerts you to water on the floor while it is still a puddle rather than a ceiling. Some models shut off the main automatically.
Neither replaces insulation and a working shutoff valve, but both catch what preparation misses. Our guide to detecting hidden water leaks covers what to watch for manually.
Signs You Need Emergency Plumbing Help
Preparation reduces the odds. It does not eliminate them. Call immediately if you notice:
Water stains appearing on ceilings or walls
A sudden drop in water pressure, which often means a line has already split
No water at all from a fixture during a freeze, which usually means that section is frozen
Banging or gurgling from inside the walls
No hot water, or water pooling near the heater
A frozen pipe that has not burst yet is the best possible time to call. Our guide on what to do during a plumbing emergency covers the first ten minutes, and we run 24/7 emergency service across the Eastside.
Frequently Asked Questions
At what temperature do pipes freeze?
The working threshold is 20°F, but uninsulated pipes in unheated spaces can freeze above that, and sustained cold matters more than a brief overnight dip. A few hours at 28°F is usually fine. Three days in the teens is not.
Should I drip hot water or cold water?
Cold, from the faucets served by exposed pipes. If you have a single-handle fixture, set it so water moves through both lines.
How much does it cost to winterize plumbing?
Doing it yourself runs to the cost of foam sleeves, caulk, and hose bib covers, usually under a hundred dollars. A professional pre-winter inspection costs far less than a single burst pipe repair. Our plumber cost guide covers typical local pricing.
Do I need to winterize if I live in Bellevue?
Yes. Mild winters are the reason, not the exception. Homes here often have supply lines running through uninsulated crawl spaces because deep freezes are rare, which means the few that do arrive cause more damage than they would somewhere colder and better built for it.
What do I do if a pipe is already frozen but has not burst?
Leave the faucet open, apply gentle heat with a hair dryer or heating pad, working from the faucet back toward the frozen section, and never use an open flame. If you cannot locate or reach it, call us before it thaws.
When should I winterize?
Finish outdoor draining and insulation by mid-October. The dripping and cabinet opening steps are for individual cold snaps, not the whole season.
Do Not Wait for the First Freeze
Everything above takes one afternoon. A burst pipe takes weeks to put right and involves a restoration crew, an insurance claim, and a hole in a wall.
Ready to get it handled? Book a winter inspection or call 425-331-2011. We will check the vulnerable runs, insulate what needs it, and make sure your shutoff valve works before you need it to.
